Process of preparing films



Patented Fee. a, 19241.

MQZJ/ll? PATENT cranes.

ALBERT F. SULZER, OF ROCHESTER, NEW YORK, ASSIGNOR TO EASTMAN KODAK COM- PANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

PROCESS OF PREPARING FILMS.

No Drawing.

To all whom it may concern:

Be it known that I, ALBERT F. SULZER, a citizen of the United States of America, residing at Rochester, in the county of Monroe and State of New York, have invented certain new and useful Improvements in Processes of Preparing Films, of which the following is a full, clear, and exact specificat1on.

This invention relates to the preparation of films, particularly those containing cellulose ethers, such as ethylcellulose or the like. One object of my invention is to reduce the shrinkage of such films when subjected to the fluid treatment ordinarilyemployed in photographic manipulation. Another object is to preshrink the film before it is coated or perforated. Other objects will hereinafter appear.-

-When film containing cellulose ethers is immersed in the usual developing, fixing and washing baths andfinally dried, it will ordinarily shrink noticeably. The shrinkage is often more than is desirable in motion picture work or in certain processes of color photography where accurate registration is desirable. This shrinkage is very largely due to the base which supports the sensitive emulsion and for convenience this base will hereinafter be referred to as the film.

In the application of Neil S. Kocher, filed Dec. 23, 1921, Serial No. 524,534 for process of preparing films, assigned to the same assignee as the present application, there is described a method of preshrinking cellulose ether film by treating it with very cold water and then drying it. This eliminates or very greatly lessens shrinkage when the film is subsequently manipulated in the ordinary photographic baths.

But under certain manufacturing conditions it is desirable to use a preshrinking method which can be carried out at ordinary or room temperatures. I have discovered that the preshrinking can be-very satisfactorily done at such temperatures by using two successive baths, instead of a single bath,

one for swelling the film and the second for shrinking it. The shrinking which follows the preliminary swell ng is much greater than the latter, so that the net result is a reduction of the film to the size which it substantially maintains during subsequent use.

By way of illustration, I will now describe my preferred method of applying the prin- Application filed October 31, 1922. Serial No. 598,202.

ciple of my invention. A bath is first prepared for swelling the film. I prefer to make this by mixing a swelling agent with water; for instance 70% of methyl alcohol may be mixed with of water. For the shrinking bath I find plain water simple and satisfactory. These baths may be kept at room temperature, a useful range being from 60 to 80 F., say F.

The film to be treated is first immersed in the swelling bath of alcohol and water until the dimensions of it have increased to a satisfactory amount. By way of example, I have found that some cellulose ether films increase roughly 10% in width and length after 2 minutes treatment in this bath. When the swelling has taken place to the degree which is desirable for the particular kind of film that is being treated, it is immersed in the water where it quickly shrinks to less than its original size. Thereafter it can be dried and used in the regular way, being subsequently coated with emulsion, formed into motion picture strips, and perforated in any usual or preferred manner. Because of the preshrinking, subsequent changes in dimensions are very much less than would be the case without pie-treatment.

The treatment may be carried out in any ordinary apparatus for fluid treating film, and the baths may be applied by immersion, spraying, or any other usual or preferred way for applying liquids to film. The shrinking does not ordinarily produce any troublesome buckling or puckering of the film. llf this tendency should, however, manifest itself, it can be prevented by holding the film flat during the shrinkage, such as by holding it under tension during the treatment. Any suitable swelling agent may be substituted for the methyl alcohol, preferably one that is miscible with water being used. have found that the other lower monohydroxy aliphathic alcohols, such as ethyl alcohol, propyl alcohol and butyl alcohol, and to a lesser degree amyl alcohol, can be employed. In general, the greater the molecular weight of the alcohol used, the greater should be its proportion in the swelling bath. Acetone is also useful.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. The method of preshrinking cellulose ether films, that are insoluble in water at ordinary temperatures but shrink after treat ment in photographic baths, which comprises the steps of first treating said films with a swelling bath and then treating them with a shrinking bath.

2. The method of preshrinking cellulose ether films, that are insoluble in water at ordinary temperatures but shrink after treatment in photographic baths, which comprises the steps of first treating said films in a mixture of a swelling agent and water, and then shrinking them in Water.

3. The method of preshrinking cellulose ether films, that are insoluble in Water at ordinary temperatures but shrink after treatment in photographic baths, which comprises the steps of first swelling said films ether films, that are insoluble in water at ordinary temperatures but shrink after treatment in photographic baths, which comprises the steps of first swelling said films in a bath comprising 70 parts of methyl alcohol to 30 parts of Water, and then shrinking them in a bath of Water.

Signed at Rochester, New York, this 24th day of October, 1922.

ALBERT F. 'SULZER, 

